Regarding standardness, I feel that Tasha's Cauldron Of Everything (TCOE) and Xanathar's Guide To Everythin (XGTE) are much more "the standard expansions" than the Sword Coast Adventurers' Guide (SCAG).
Fair point, I think I mostly meant prioritizing older ("established") source books that are less debated in my personal circles. I.E. some of the power creep in Tasha's is still discussed with some DMs banning Twilight & Peace domains completely. But you're probably right that people are likely more familiar with those compared to SCAG. Turns out the only SCAG subclass I ended up picking was Swashbuckler anyways
I do like your idea with psionic-flavored subclasses, and I honestly hope they lean into that more with the Great Old One warlock as well.
As for accounting for game mechanics, that was in the back of my head a bit, but not top of mind for this particular post.
